Method for improving the centering of stamping matrices for sound and video discs

ABSTRACT

The care and accuracy of centering the negative, e.g. the master or stamping matrix, used in the production of sound and video record discs is improved by preparing the original lacquer foil record so that the negative will have a profile which extends centrically to the record groove spiral. This is accomplished by inserting a centering core, which is adapted to the spindle of the playback system and has a laterally extending flange defining a galvanically reproducible centering edge, into a centering hole in the foil prior to the cutting of the spiral groove containing the recorded information into the lacquer foil.

United States Patent Knothe et al.

[ July 31, 1973 METHOD FOR IMPROVING TIIE CENTERING OF STAMPING MATRICES FOR SOUND AND VIDEO DISCS [75] Inventors: Herbert Knothe, Neumunster; Klaus Roschmann, Nortorf; Werner Rohwer, Ellerdorf/Uber Nortorf, all of Germany [73] Assignee: Teldec Telefunken-Decca Schallplatten G.m.b.I-I., Hamburg, Germany [22] Filed: Nov. 23, 1971 [21] Appl. No.: 201,380

[30] Foreign Application Priority Data Nov. 23, 1970 Germany P 20 57 478.1

[52] US. Cl. l78/6.6 B, 274/42 R, 274/46 [51] Int. Cl. ..G1lb 3/64, Gllb 3/70 [58] Field of Search 274/42 R, 46, 3; 17816.6 B

[56] References Cited UNITED STATES PATENTS 1,755,743 4/1930 Morrison 274/42 R OTHER PUBLICATIONS Audio Cyclopedia, 1969, p. 655, 659, 660, 671, relevant to centering lacquer foil originals.

Hansen 274/42 R [57] ABSTRACT The care and accuracy of centering the negative, e.g. the master or stamping matrix, used in the production of sound and video record discs is improved by preparing the original lacquer foil record so that the negative will have a profile which extends ccntrically to the record groove spiral. This is accomplished by inserting a centering core, which is adapted to the spindle of the playback system and has a laterally extending flange defining a galvanically reproducible centering edge, into a centering hole in the foil prior to the cutting of the spiral groove containing the recorded information into the lacquer foil.

4 Claims, 1 Drawing Figure METHOD FOR IMPROVING THE CENTERING OF STAMPING MATRICES FOR SOUND AND VIDEO DISCS BACKGROUND OF THE INVENTION The present invention relates to the centering of stamping matrices for pressing record discs containing sound and video recordings. More particularly, the present invention relates to an improved method of manufacturing phonograph records whereby the ease of centering and the centering accuracy of the stamping matrix is improved.

It is known in the phonograph record art to place stamping matrices which have been produced by galvanic means, either directly or indirectly, from an original into a special die in which the matrices are centered with regard to the spiral groove thereon by means of a measuring device which usually comprises a microscope. The stamping matrices are then provided, in the aligned position, with a centric center hole which accommodates a holding device in the pressing mold. The use of the center hole as the sole centering means for the matrices is often unsuitable since frequent changing can cause the center hole to become noncircular.

Another known method of centering the stamping matrix is to align same according to the concentric trailing groove thereon. In this method the accuracy of the centering is improved since it is not necessary, as in the first method, to compensate intuitively for the spiral shape of the groove.

An improvement for the centering of stamping matrices is described in German Offenlegungsschrift (Laidopen Application) No. 1,809,632. According to this method a lacquer foil is provided with a central bore whicch must fit on the takeup pin of the recording or cutting machine with the least amount of play so that as little eccentricity as possible is produced with respect to the bore when the spiral groove is subsequently cut.

The lacquer foil original produced in this manner is then made conductive by metallizing the lacquer foil through electrolysis. After this process step a hollow centering core is inserted into the bore with as little play as possible and a negative, Le, a master or a stamping matrix respectively, is then made galvanically or chemically in a well known manner.

In this process a number of manual influencing and error producing possibilities exist which are not tenable for accurate processing, e.g. in the production of video records. These errors basically reside in the extent to which it is possible to make the bore in the very thin aluminum carrier of the lacquer foil to fit perfectly over the takeup pin or spindle of the cutting or recording machine and the fact that the centering core must be made to fit exactly into the bore in the foil. Additionally, the insertion of the centering core after the reduction silver plating also makes possible the occurrence of errors since a slight tilting of the core during insertion can result in undesirable eccentricity.

SUMMARY OF THE INVENTION The present invention now relates to a centering method which permits more accurate centering of the stamping matrices than was heretofore possible with the known methods in that before the cutting of the spiral groove, the lacquer foil is prepared so that the negatives, i.e., the masters or stamping matrices, respectively, are provided with a profile which extends centrically to the groove spiral and which simultaneously serves to hold the negatives in the pressing mold. The desired profile for the negatives is provided in a galvanoplastic manner.

The above desired result is achieved according to the present invention in that in a method for producing a negative from a lacquer foil for the production of sound and video discs, the lacquer foil used to produce the original is initially provided with a central hole, a hollow centering core, which is adapted to the takeup pin of the playback system and is provided with a laterally extending galvanically reproduceable centering edge, is inserted into the central hole of the lacquer foil. The lacquer foil with the centering core is then placed on the recording machine and a groove spiral containing the recorded information is cut into the lacquer foil, and thereafter, in a known manner, a negative, i.e., a master or a stamping matrix, respectively, is obtained from the lacquer foil either chemically or galvanoplastically.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a sectional view of a lacquer foil provided with a centering core according to the method of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the figure there is shown a lacquer foil 1 which is provided with a central hole 2. Prior to the cutting of the spiral groove 7, a hollow core 3 having a bore 4 and a laterally extending flange 5, the edge of which forms a galvanically reproducible centering edge 5', is inserted into the central hole 2. The bore 4 must be concentric with the centering edge 5 and must fit on the takeup pin or spindle 6 of the cutting or recording machine (not shown) with the least possible amount of play so that as little eccentricity as possible is produced for the groove sprial 7 with respect to the centering edge 5' during subsequent cutting of the groove spiral 7. After cutting of the spiral groove to form the original disc recording, a negative thereof, i.e., a master or a stamping matrix, respectively, are produced from the lacquer foil in a known manner either galvanically or chemically.

The hollow centering core 3 is inserted into the uncut lacquer foil 1 in any suitable desired manner, for example, by screwing or gluing. The size or accurate position of the central hole 2 in the lacquer foil 1 now plays only a subordinate role, i.e., it now serves only to hold the hollow centering core 3. The fitting hole or bore 4 of the core 3 which extends concentrically to the centering edge 5' and which is adapted to the takeup pin or spindle of the playback apparatus is used for the cutting process. The diameter of the bore 4 corresponds to the diameter of spindle of the playback system.

The use of the method according to the invention results in far fewer error possibilities than was possible in the methods according to the prior art since the core 3 remains in the foil 1 during all of the subsequent galvanic processes. The hollow centering core 3 is cleaned together with the lacquer foil 1 and prepared for the reduction silver plating.

Since in the described method of the invention lacquer foil 1 and the hollow centering core 3 constitute a single unit, care must be taken that the lacquer foil 1 and the hollow centering core 3, which is predominantly made of refined steel, are simultaneously cleaned and sensitized in such a manner that a finegrained ductile metal layer can be chemically deposited in order to form the negative.

The cleaning and sensitizing of these different materials is advisably effected in a single bath which is geared in its composition to the properties and the type of soiling of the two materials. The cleaning and sensitizing can additionally be done untrasonically so that with a change in the rotational speed (convection) of the lacquer foil 1 in thee cleansing bath, the cavitation hardness can be set in dependence on the degree of soiling of the lacquer foil and the core. It is moreover advisable to provide the bath with a continuous filtration system in order to remove ejected dirt particles immediately.

The composition of a cleaning bath which may be used to simultaneously clean the foil 1 and the core 4 may comprise, for example, a solution of tinchloride, hydrochloric acid, grape sugar and saponine. The lacquer foil 1 and core 4 remains for example, in such a cleaning bath for about 2 minutes.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meansing and range of equivalents of the appended claims.

We claim:

1. ln a method for producing a negative from a lacquer foil original for the manufacture of record discs containing sound or video recordings, wherein the negative, i.e., a master or a stamping matrix,is formed from the lacquer foil original recording, in a known manner, either chemically or galvanically, the improvement comprising the steps of: providing the lacquer foil with a centering hole; inserting a hollow centering core, which is adapted to the spindle of the playback system and which is provided with a laterally extending flange defining a galvanically reproduceable centering edge, into said centering hole; cutting a groove spiral containing the recording into the lacquer foil; and then forming the negative from the lacquer foil whereby the negative will include the profile of the laterally extending flange which profile can then be used to center the negative during subsequent processing.

2. The method for producing negatives for the manufacture of video or sound record discs as defined in claim 1 including the step of simultaneously cleansing and sensitizing the lacquer foil and centering core in a combined bath after the step of cutting of a spiral groove and prior to thee step of forming the negative.

3. The method for producing negatives for the manufacture of video and sound record discs as defined in claim 2 wherein the cleansing and sensitizing is additionally effected by means of ultrasonic cleaning.

4. In a method for producing a negative from a lacquer foil original recording for the manufacture of record discs containing sound or video recordings, wherein the negative, i.e., a master or a stamping matrix, is formed from the lacquer foil original recording, in a known manner, either chemically or galvanically, the improvement comprising the steps of: providing the lacquer foil with a centering hole; providing a hollow centering core having an inner diameter which corresponds to the diameter of the spindle of the playback system and a laterally extending flange defining a concentric galvanically reproducible centering edge; inserting the centering core into the centering hole with the flange extending along the surface of the lacquer foil on which the recording is to be made; cutting a groove spiral containing the recording into the lacquer foil; and then forming the negative from the original, whereby the negative will include the profile of the laterally extending flange which profile can then be used to center the negative during subsequent processing.

* t i i 

1. In a method for producing a negative from a lacquer foil original for the manufacture of record discs containing sound or video recordings, wherein the negative, i.e., a master or a stamping matrix,is formed from the lacquer foil original recording, in a known manner, either chemically or galvanically, the improvement comprising the steps of: providing the lacquer foil with a centering hole; inserting a hollow centering core, which is adapted to the spindle of the playback system and which is provided with a laterally extending flange defining a galvanically reproduceable centering edge, into said centering hole; cutting a groove spiral containing the recording into the lacquer foil; and then forming the negative from the lacquer foil whereby the negative will include the profile of the laterally extending flange which profile can then be used to center the negative during subsequent processing.
 2. The method for producing negatives for the manufacture of video or sound record discs as defined in claim 1 including the step of simultaneously cleansing and sensitizing the lacquer foil and centering core in a combined bath after the step of cutting of a spiral groove and prior to thee step of forming the negative.
 3. The method for producing negatives for the manufacture of video and sound record discs as defined in claim 2 wherein the cleansing and sensitizing is additionally effected by means of ultrasonic cleaning.
 4. In a method for producing a negative from a lacquer foil original recording for the manufacture of record discs containing sound or video recordings, wherein the negative, i.e., a master or a stamping matrix, is formed from the lacquer foil original recording, in a known manner, either chemically or galvanically, the improvement comprising the steps of: providing the lacquer foil with a centering hole; providing a hollow centering core having an inner diameter which corresponds to the diameter of the spindle of the playback system and a laterally extending flange defining a concentric galvanically reproducible centering edge; inserting the centering core into the centering hole with the flange extending along the surface of the lacquer foil on which the recording is to be made; cutting a groove spiral containing the recording into the lacquer foil; and then forming the negative from the original, whereby the negative will include the profile of the laterally extending flange which profile can then be used to center the negative during subsequent processing. 